Had some highway driving today on my way to pick up my
new FEH 
.
Since they sold it while I was on my way I had a long soulful drive back
.
Being kinda bummed as you'd expect I could care less how my tank average suffered, so I decided to do some testing, and found out some neat stuff.
Check it out... DWL based on IGN 15 @ 55mph & 68mpg
Now that's a highway castle I would have killed for a year ago! So here's what I saw. Keeping IGN pegged at 15 (or anything) I saw RPM all over the map. RPM would drop as I slowed down (going up hill) and rise as I speed up (going down hill). The IGN wants to chase the RPM's up or down so you will have to ease up (a hair) on decent, and add pressure (slight) on climbs. The cool thing is that this feels a lot more like a "don't move your foot" approach. My position on the gas pedal was darn near rock solid while trying to hold IGN15. Worse driving cramps ever.
So here's a WAG on DWL average speeds as they map to IGN:
| __IGN__ | __Avg MPH__ | __Avg MPG__ |
|
13.0 | 45 | 80 |
|
13.5 | 47 | 75 |
|
14.0 | 50 | 73 |
|
14.5 | 53 | 70 |
|
15.0 | 55 | 68 |
|
15.5 | 57 | 65 |
|
16.0 | 60 | 63 |
|
16.5 | 63 | 60
|
Again, this is a guess but I think it approaches what everyone is reporting. If my understanding of ignition timing is correct (not sure it is), there should be inherent inefficiencies (albeit small) that are introduced with changing ignition timings while driving. What I find interesting is how much RPM varies with a constant ignition timing as speed varies.
So (assumptions on assumptions here) it's possible that DWL when holding RPM may be causing IGN to bounce around a lot, introducing loss. What surprised me honestly is how constant the castle bars were when using DWL on IGN. That and the fact that it really is feedback on how to keep your pedal position rock solid.
Anyway 65 @ 65 may not be possible, but 60 @ 60 may have a chance at happening.
Edit: For the above, AC on AUTO at 77 headlights on.
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